A light valve projector projects a bright light source through an electro-optical system that receives electronic image information and produces a projected optical image. Light-valve projectors are rapidly converting to matrix driven arrays; examples being active matrix LCD projectors such as the projector disclosed in U.S. Pat. Nos. 5,231,432 and 6,086,208, and the so-called “DLP” display of Texas Instruments Company which uses technology originating from the type of solid state light modulator disclosed in U.S. Pat. No. 3,882,271.
One prior approach describes a solid state light modulator which employs a reflective patterned alignment modulator in a projector having a schlieren optical system. There is a drawback to this system, however. In order to get a high contrast ratio, the schlieren lens needs to have an extremely good non-reflective coating. For transmissive schlieren optics this is not a serious problem, since it takes two reflections from lens surfaces to reduce contrast. With a reflective system, however, only one reflection reduces contrast.
It is among the objects of the present invention to overcome disadvantages of prior art approaches, and to devise an improved method and apparatus for projection of images using solid state light modulation. It is among the further objects of the present invention to provide an improved single modulator color projector that employs color selection by diffraction.